Danfoss VLT AQUA Programming Manual page 181

®
VLT AQUA Drive Programming Guide
2.17.4. 20-7* PID Auto-Tuning
The frequency converter PID Closed Loop controller (parameters 20-**, FC Closed Loop) can be
auto-tuned, simplifying and saving time during commissioning, whilst ensuring accurate PID con-
trol adjustment. To use Auto-tuning it is necessary for the frequency converter to be configured
for Closed loop in par 1-00 Configuration Mode.
A Graphical Local Control Panel (LCP) must be used in order to react on messages during the auto-
tuning sequence.
Enabling Auto-tuning par 20-75
then directs the user with on-screen instructions.
The fan/pump is started by pressing [Auto On] button on the LCP and applying a start signal. The
speed is adjusted manually by pressing the [ ] or [ ] navigation keys on the LCP to a level where
the feedback is around the system setpoint.
PID Auto-tuning functions by introducing step changes whilst operating at a steady state and then
monitoring the feedback. From the feedback response, the required values for par 20-93 PID
Proportional Gain and par 20-94 Integral Time are calculated. Par 20-95 PID Differentiation Time
is set to value 0 (zero). Par. 20-81 PID Normal / Inverse Control is determined during tuning
process.
These calculated values are presented on the LCP and the user can decide whether to accept or
reject them. Once accepted, the values are written to the relevant parameters and Auto-tuning
mode is disabled in par 20-75.Depending on the system being controlled the time required to carry
out Auto-tuning could be several minutes.
20-70 Closed Loop Type
Option:
*
[0]
[1]
[2]
[3]
[4]
, puts the frequency converter into Auto-tuning mode. The LCP
NB!
It is not possible to run the motor at maximum or minimum speed, when manually
adjusting the motor speed due to the need of giving the motor a step in the speed
during autotuning.
Function:
Auto
Fast Pressure
Slow Pressure
Fast Temperature
Slow Temperature This parameter defines the application response. The default
mode should be sufficient for most applications. If the applica-
tion response speed is known, it can be selected here. However,
it is preferable to select a slow rather than fast setting, as if a
fast setting is selected, the auto-tune may fail to wait for a
®
MG.20.O2.02 - VLT is a registered Danfoss trademark
NB!
The setpoint reference entered here is added to
any other references that are enabled (see par.
group 3-1*).
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2. Parameter Description
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